For the first time, scientists have explained why larger dogs live shorter lives than smaller dogs: selective breeding for size has created large breeds more vulnerable to cancer.
The reasons of differences in lifespan and death in 164 dog breeds ranging in size from chihuahuas to Great Danes were investigated by specialists at the University of Adelaide.
When these data sets were analyzed, authors revealed that larger dogs were more likely to die from cancer at a younger age than smaller dogs, according to Dr. Jack da Silva of the University of Adelaide's School of Biological Sciences.
Larger dogs did not necessarily age faster than smaller breeds, but the study found that as the breed's average body weight increased, so did cancer rates.
Larger Dogs Live As Long As Smaller Breeds
PHILIP FONG/AFP via Getty Images
For the first time, scientists have explained why larger dogs live shorter lives than smaller dogs: selective breeding for size has created large breeds more vulnerable to cancer, as per Phys.org.
The reasons of differences in lifespan and death in 164 dog breeds ranging in size from chihuahuas to Great Danes were investigated by specialists at the University of Adelaide.
According to Dr. da Silva, the focus in all organisms is on reproducing early, even if it means foregoing body maintenance and repair and living longer.
Dogs are an excellent model for studying human aging. Dogs, like humans in the industrialized world, live in an environment that protects them from accidental and infectious causes of death, making them more susceptible to age-related diseases such as cancer.
Although the survey results may be concerning for large dog owners, the researchers predict that larger breeds will evolve to develop better cancer-fighting genes.
The majority of the 400 or so dog breeds we know today have only been around for about 200 years.
Larger dogs haven't had enough time to develop cancer-fighting mechanisms to match their size. This could still happen, but at a cost to reproduction, according to Dr. da Silva.
Dr. da Silva predicts that larger breeds will adapt and live longer lives, but that due to the theory of aging, they will have smaller litter sizes in the future.
This could happen naturally or through selective breeding, as people focus on breeding larger dogs with lower cancer rates and thus longer lifespans.
It manifests as a solid swelling in the affected area, such as a limb or the skull, and can rapidly spread to any other part of the body, as per Epigram.
The tumor may cause a pathological fracture, which occurs when a bone breaks due to disease rather than injury.
This cancer is frequently accompanied by restlessness or lameness, as well as a high temperature and limping.
As a result, it is critical to keep an eye out for subtle changes in the dog's behavior, such as not eating or a change in temperament, to allow for early diagnosis.
The University of Bristol Veterinary School led a study with Cardiff University and the Royal Veterinary College London to compare 1,756 confirmed cases of osteosarcoma in various dog breeds to a total of 905,211 dogs in general veterinary care (in 2016).
Rottweilers, Great Danes, Rhodesian Ridgebacks, and Mastiffs were among the 27 breeds found to have a higher risk of osteosarcoma than crossbreds.
According to the researchers, 'heavier dogs with longer legs and longer skull shapes' are at the highest risk of developing bone cancer.
This research has been invaluable in confirming the genetic basis of osteosarcoma in dog breeds, not only for improving the quality of life for affected dogs but also for using affected dogs as study models for how these tumors may develop in humans.
The future of this research could focus on identifying specific gene mutations linked to this cancer in the hopes of better understanding the biological pathways that lead to tumor formation in normal bone tissue.
Individual genes discovered in specific breeds could be targeted by newly developed drugs in future treatments.
